The overall goal of this project is to define neuropeptide pathways involved in the control of food intake in primate species. Using rhesus monkeys as an experimental model, agonists and antagonists of various peptides, hypothesized to influence food intake, are being tested to determine how they modulate food intake in primates, their time-course of action, and their interaction with other peptide systems. The current focus of this project is on understanding the role of Neuropeptide Y (NPY) and melanocortin peptides on the control of food intake.